Medical charged particle irradiation apparatus

ABSTRACT

A medical charged particle irradiation apparatus capable of irradiation from upward and horizontal directions and performing a preparing/ascertaining work without any separate device such as a moving capsule or the like comprising a patient&#39;s bed, on which a patient lies, a transport equipment for injecting and transporting charged particle beams toward the patient&#39;s bed, an irradiation field forming device for forming an irradiation field for the beams transported by the transport equipment, and a gantry provided to be rotatable about an axis of rotation, and wherein the irradiation field forming device is eccentrically arranged such that an axis of irradiation passes a position different from the axis of rotation, and the patient&#39;s bed is arranged on an opposite side of the transport equipment to a plane, which contains the axis of rotation and is substantially perpendicular to the axis of irradiation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a medical charged particle irradiationapparatus for using charged particles to treat cancer, lump and so on.

2. Description of the Related Art

A medical charged particle irradiation apparatus for irradiating chargedparticles such as proton, carbon ion, or the like on an affected part ofa patient to treat cancer, lump and so on injects charged particles,which are generated in an ion source and accelerated by a synchrotron orthe like, to guide the same to an irradiation field forming meanscontaining a collimator or the like, and irradiates the chargedparticles on a patient lying below the irradiation field forming meansafter an irradiation field conformed to a configuration of the affectedpart is formed in the irradiation field forming means.

At this time, a patient ordinarily lies on a patient's bed with the faceupward, and it is necessary to perform irradiation from an appropriateangular position (for example, from upward or from substantiallyhorizontally, or the like) in accordance with position and state of theaffected part. Also, exposure dose from various directions is suppressedwhile irradiation is made on the affected part from a plurality ofdirections (multiple-field), whereby there is produced an effect that apredetermined exposure dose on the affected part can be achieveddepending upon a weight of the part and exposure dose on other portionsthan the affected part can be lowered to reduce unnecessary exposure.

For example, Japanese Patent Laid-Open No. 192419/1993 describes arotary irradiation therapeutic device as a prior art taking account ofthe above. This device comprises a substantially cylindrical-shapedrotary frame, an outer periphery of which is rotatably supported byrollers, and which mounts therein transport means (deflecting device andvacuum duct), irradiation field forming means (beam adjusting device),and an irradiation chamber provided with a patient's bed (irradiationbed). The transport means injects charged particle beams at adiametrically central portion of the rotary frame to transport the sameto the irradiation field forming means while swinging up the same towarda diametrically outer periphery. The irradiation field forming means isarranged on a diameter passing an axis of rotation of the rotary frameto cause beams to be injected diametrically inwardly of the rotary framefrom a distal end of the transport means arranged on the outer peripheryof the rotary frame and to form an irradiation field for the beams tocause the beams to be injected into the irradiation chamber. Theirradiation chamber is rotatably (turnably on its axis) arranged (inother words, rotatable about an axis of rotation of the rotary frame) ona beam emission side position of the irradiation field forming means inthe rotary frame to constantly maintain the patient's bed substantiallyhorizontal irrespective of a rotating position of the rotary frame.

With such construction, in the case where it is desirable to irradiatebeams from, for example, above the affected part in accordance withposition and state of the affected part, the rotary frame is turned toposition the transport means on an upper side and the irradiationchamber on a lower side to cause beams having been swung upsubstantially vertically upward from the diametrically central portionof the rotary frame to be passed downward to be irradiated on thepatient's bed in the irradiation chamber disposed below the irradiationfield forming means from above. Also. in the case where it is desirableto irradiate beams from, for example, laterally (horizontal direction)of the affected part, the rotary frame is turned to position thetransport means on one lateral side (for example, lefthand) and theirradiation chamber on the other lateral side (for example, righthand)to cause beams having been swung up leftward from the diametricallycentral portion of the rotary frame to be passed horizontally fromlefthand to righthand to be horizontally irradiated on the patient's bedin the irradiation chamber disposed rightwardly of the irradiation fieldforming means.

However, the above prior art involves the following problems.

That is, the prior art provides a construction, in which the rotaryframe provided with the irradiation chamber capable of turning on itsaxis is turned in order to irradiate beams from above and in ahorizontal direction in accordance with a position of the affected partor the like as described above. As a result, a heightwise position ofthe patient's bed is considerably varied as the irradiation chambermakes a circular motion (vertical movement) due to turning of the rotaryframe. Concretely, since a rotating irradiation body provided with thetransport means and the irradiation field forming means has a turningdiameter of, for example, around 5 m, a distance, over which thepatient's bed rises from a lowest position for irradiation from above toa lateral position for irradiation from horizontal irradiation, amountsto about 2.5 m corresponding to a radius of rotation.

With the above prior art, a moving capsule capable of following thepositional variation of the patient's bed is separately provided injuxtaposition to one sense of an axial direction of the rotary frame tocope with the situation, and a physician (or a technician) performingthe irradiation preparing/ascertaining work can get on the movingcapsule to easily reach a position of the patient's bed for improvementin convenience. However, because of the need of providing such movingmechanism as the moving capsule separate from the rotary frame, theentire device becomes large in size (in particular, in the axialdirection of the rotary frame) and the mechanism is made complex.

SUMMARY OF THE INVENTION

An object of the invention is to provide a medical charged particleirradiation apparatus capable of irradiation from upward and horizontaldirections and performing a preparing/ascertaining work without theprovision of any separate moving mechanism such as a moving capsule orthe like.

(1) In order to attain the above object, the invention provides amedical charged particle irradiation apparatus for irradiating chargedparticles on an affected part of a patient, comprising a patient's bed,on which a patient lies, a transport equipment for injecting andtransporting charged particle beams toward the patient's bed, anirradiation field forming means for forming an irradiation field for thebeams transported by the transport equipment, and a rotating irradiationbody provided to be rotatable about an axis of rotation, and wherein theirradiation field forming means is eccentrically arranged such that anaxis of irradiation thereof passes a position different from the axis ofrotation, and the patient's bed is arranged on an opposite side of thetransport equipment to a plane, which contains the axis of rotation andis substantially perpendicular to the axis of irradiation.

In the case where it is desirable to enable irradiation from above tolaterally (a substantially horizontal direction) in a state, in which apatient lies with the face upward, an irradiation device capable ofvarying a direction of irradiation from upward to either of right andleft senses in a substantially horizontal direction (in other words,variable in the range of, for example, 90°) relative to an affected partwill do provided that irradiation is performed with a head and feetreversed when a patient lies.

In consideration in the variable range of 90°, with the above prior art,the patient's bed is in a lowest position at the time of upwardirradiation and in a lateral position at the time of horizontalirradiation where the rotating irradiation body is turned 90° with theresult that a distance, over which the patient's bed rises from thelowest position to the lateral position amounts to, for example, about2.5 m substantially corresponding to a radius of the rotatingirradiation body.

In contrast, according to the invention, the axis of irradiation of theirradiation field forming means is made eccentric so as to pass adifferent position from the center of rotation (in other words, the axisof irradiation involves a predetermined angle so as not to intersect thecenter of rotation), whereby a position of the patient's bed at the timeof upward irradiation is not a lowest position as in the above prior artbut can rise an amount, which correspond to the above eccentricity,somewhat to a position in either direction laterally of the lowestposition. Also, a position of the patient's bed at the time ofhorizontal irradiation can be correspondingly made a position somewhatlower than the other lateral position unlike the lateral position (theother lateral position in accordance with the above) in the above priorart. That is, the patient's bed 8 when the rotating irradiation body isturned to displace the patient's bed from a position at the time ofupward irradiation to a position at the time of horizontal irradiationmoves from the position at the time of upward irradiation→graduallydescends to a lowest position→gradually ascends to a position at thetime of horizontal irradiation. In this manner, since the position ofthe patient's bed at the time of upward irradiation and the position ofthe patient's bed at the time of horizontal irradiation are not a lowestposition but can be made a position somewhat higher than the lowestposition, variation (in other words, difference of height between thelowest position and the position at the time of upward irradiation orthe position at the time of horizontal irradiation) of a heightwiseposition of the patient's bed in displacements, that is, the position atthe time of upward irradiation→the lowest position→the position at thetime of horizontal irradiation can consequently be suppressedconsiderably.

Meanwhile, in the rotating irradiation body, the transport equipmenthaving charged particle beams injected at, for example, a diametricallycenter (axis of rotation of the rotating irradiation body) once directs(swings up) the beams to a diametrically outer peripheral side, thentransports the beams a predetermined distance in the axial direction ofrotating irradiation body, and again directs the beams to thediametrically inner peripheral side of rotating irradiation body at adistal end to inject the beams into the irradiation field forming means.A plurality of deflecting electromagnets for directing (deviating) thebeams are provided on the beam transport path.

With such construction, in the case where the patient's bed is arrangedat the center of rotation of the rotating irradiation body, and theirradiation field forming means is arranged on the diametrically outerperipheral side thereof, a distal end of the transport equipment ispositioned near the diametrically outer peripheral side thereof than theirradiation field forming means in order to inject beams into theirradiation field forming means. As a result, the transport means isshaped to be considerably enlarged toward the diametrically outerperipheral side of the rotating irradiation body, so that the rotatingirradiation body is increased in diameter of rotation.

Hereupon, according to the invention, the patient's bed is arranged onan opposite side of the transport means to the axis of rotation, morespecifically, on an opposite side of the transport means to a plane,which contains the axis of rotation and is substantially perpendicularto the axis of irradiation. Thereby, the irradiation field forming meanscan also be made offset an amount, by which the patient's bed is offsettoward the opposite side of the transport means, toward the oppositeside of the transport means, with the result that the above enlargementtoward the diametrically outer peripheral side thereof can be reduced.As a result, the rotating irradiation body can be reduced by such amountin diameter of rotation.

As described above, according to the invention, the above action ofreducing the rotating irradiation body in diameter of rotation is addedto the action of suppressing heightwise variation in a position of thepatient's bed between the position at the time of upward irradiation andthe position at the time of horizontal irradiation, whereby theirmultiplied effect can suppress heightwise variation of the patient's bed(difference of height) to, for example, around 1.5 m at maximum throughsuitable setting of positions of respective parts such as eccentricdimension or the like. Thereby, even in a state, in which the patient'sbed is in the highest position (for example, the position at the time ofupward irradiation or the position at the time of horizontalirradiation), a physician or a technician can perform an irradiationpreparing/ascertaining work or the like while standing on a floorwithout the use of any specific device, so that convenience can beconsiderably improved. Also, since the heightwise position of thepatient's bed is suppressed, a patient can be enhanced in safety.

(2) In the above paragraph (1), the patient's bed is preferablyrotatably suspended and supported by the irradiation field formingmeans.

Thereby, the patient's bed can be maintained horizontal by suitablyturning the patient's bed in accordance with a rotating position of therotating irradiation body. Also, there is produced an effect that therelative positional accuracy between a target point of an affected partand an actual irradiation point at the time of irradiation can bemaintained high.

(3) In the above paragraph (2), a heavy object is more preferablyprovided on the patient's bed to maintain a posture thereofsubstantially horizontal.

Thereby, since a center of gravity of the patient's bed can be madelower than a position of suspension, the bed can be easily maintainedhorizontal. Also, the bed is made heavy whereby it is possible tofulfill the function of a counter weight for the transport means withrespect to the axis of rotation of the rotating irradiation body.

(4) In the above paragraph (2), there are more preferably provided beddriving means for driving the patient's bed, which is rotatablysuspended from and supported, to change its inclination, inclinationdetecting means for detecting inclination of the patient's bed, andinclination controlling means for controlling the bed driving means inaccordance with results of the detecting means.

Thereby, it becomes possible to forcedly and surely maintain the bedhorizontal or at a predetermined angle.

(5) In the above paragraph (1), there are more preferably provided arotating shaft member fixed to the rotating irradiation body, a centralaxis of which shaft member constitutes the axis of rotation, and supportmeans for rotatably supporting the rotating shaft member.

With a construction, in which the axis of rotation of the rotatingirradiation body is constituted by the rotating shaft member, it ispossible to considerably decrease deformation, such as flexure or thelike, due to a weight of large-sized heavy elements such as thetransport means, the irradiation field forming means, or the like, ascompared with the case where such large-sized heavy elements aresupported by a substantially cylindrical-shaped rotary frame providedwith no shaft. Thereby, it is possible to prevent that degradation inrelative positional accuracy between the target point and theirradiation point, which is attributable to the flexure or the like andto achieve improvement in accuracy of irradiation. Also, theconstruction provided with a shaft enables a shaft member to supportload of all the elements of the rotating irradiation body whereby adiametrical dimension of the rotating irradiation body can be decreasedas compared with the case of supporting by means of the substantiallycylindrical-shaped rotary frame provided with no shaft.

(6) In the above paragraph (5), there are more preferably providedrotating drive means for rotatingly driving the rotating shaft member,rotation detecting means for detecting a position of rotation of therotating shaft member, and rotation controlling means for controllingthe rotating drive means in accordance with results of the detectingmeans.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing an entire schematic construction of amedical charged particle irradiation apparatus according to anembodiment of the invention;

FIG. 2 is a conceptional view showing an entire constitution of acharged particle irradiation therapeutic system provided with themedical charged particle irradiation apparatus of FIG. 1;

FIG. 3A is a view illustrating a state, in which vertical irradiation isperformed;

FIG. 3B is a view illustrating a state, in which horizontal irradiationis performed;

FIG. 4 is a view showing a detailed constitution related to rotatingdriving of a gantry and an essential part of the constitution shown inFIG. 1;

FIG. 5 is an enlarged view of a B part shown in FIG. 2, representativeof a detailed support construction for a patient's bed;

FIG. 6A is a view illustrating a construction near a connection betweena patient's bed and an irradiation field forming apparatus at the timeof vertical irradiation;

FIG. 6B is a construction drawing representative of the constructionnear the connection between the patient's bed and the irradiation fieldforming apparatus at the time of horizontal irradiation;

FIG. 7 is a conceptional view showing a path of beams in the gantry;

FIG. 8A is a conceptional view showing a comparative example, in which apatient's bed is arranged in a position of an axis of rotation of agantry in a rotary frame; and

FIG. 8B is a conceptional view showing a comparative example, in whichan axis of irradiation passes an axis of rotation of a gantry.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the invention will be described below with reference tothe drawings.

FIG. 2 is a conceptional view showing an entire constitution of acharged particle irradiation therapeutic system provided with a medicalcharged particle irradiation apparatus according to an embodiment.

In FIG. 2, with the irradiation therapeutic system, charged particlebeams (referred below to as beams) having been accelerated by a chargedparticle generating device (=acceleration device; in this example, asynchrotron but may be other acceleration devices such as cyclotron orthe like) 101 in accordance with a treatment plan mapped out in atreatment planning device 103 and under the control of a control device100 are output by an irradiation device 102 to be irradiated on anaffected part of a patient K. The irradiation device 102 rotates aboutan axis of rotation (described later) to be able to irradiate beams onthe affected part from a plurality of directions.

(1) Construction of a Synchrotron 101

The synchrotron 101 comprises a high-frequency applying device 111 forincreasing a betatron oscillation amplitude of beams through applicationof high-frequency magnetic field and electric field (referred below toas high-frequency electromagnetic field) to beams, deflectingelectromagnets 112 for bending orbits of beams, four-pole electromagnets113 for controlling betatron oscillation of beams, six-poleelectromagnets 114 for exciting resonance at the time of beam emission,a high-frequency accelerating cavity 115 for giving energy, that is,accelerating beams, an injector 116 for injecting beams into thesynchrotron 101, and emission deflectors 117 for emitting beams from thesynchrotron 101.

When the control device 100 issues an emission command to apreaccelerator 104, the preaccelerator 104 correspondingly emits beamsof low energy, which beams are conducted to the injector 116 of thesynchrotron 101 via a beam conveying system to thereby be injected intothe synchrotron 101. The injected beams are bent in path by thedeflecting electromagnets 112 to go around within the synchrotron 101.At this time, beams go around within the synchrotron 101 while beingcaused the four-pole electromagnets 113 to make betatron oscillation,the number of which is suitably controlled by quantity of excitation ofthe four-pole electromagnets 113 whereby beams go around stably withinthe synchrotron 101. The high-frequency accelerating cavity 115 appliesa high-frequency electric field to beams in the course of going-aroundwhereby energy is given to beams to accelerate the beams, so that energyis increased.

When energy of beams going around within the synchrotron 101 isincreased to a predetermined energy E, application of energy to beams bythe high-frequency accelerating cavity 115 is stopped, beams are variedin orbital gradient under the known control with the four-poleelectromagnets 113, the six-pole electromagnets 114 and thehigh-frequency applying device 111 to cause resonance to rapidlyincrease the betatron oscillation amplitude, and the emission deflectors117 cause the synchrotron 101 to emit beams.

In the above operation of the synchrotron 101, the control device 100determines energy E of beams irradiated on the affected part alongpredetermined directions of irradiation (irradiated in a plurality ofdirections) on the basis of a depth of the affected part input from thetreatment planning device (described in detail later) 103. Also,patterns of values of current fed to each of the deflectingelectromagnets 112, the four-pole electromagnets 113, and thehigh-frequency accelerating cavity 115 and required for acceleratingbeams to energy E in the synchrotron 101, and values of current fed tothe high-frequency applying device 111 and the six-pole electromagnets114 and required for emitting beams of energy E are calculated. Therespective values of current as calculated correspond to energy E everydevice to be stored in a storage means in the control device 100 to beoutput to a power source 108 or a power source 109 at the time ofacceleration and at the time of emission.

(2) Construction of an Irradiation Device 102

An essential part of the invention relates to an irradiation device 102.Details of the device will be sequentially described.

FIG. 1 is a front view showing an entire schematic construction of theirradiation device 102 (however, a motor 9 for rotary driving of agantry described later and its peripheral construction are omitted fromthe figure). In FIGS. 1 and 2, the irradiation device 102 comprises agantry (rotary irradiation body) 1 provided with a transport equipment4, an irradiation field forming device 5 and a rotating supportstructure 3, a rotating rod 13, which is fixed to the gantry 1 and whosecentral axis defines a center 2 of rotation (axis of rotation) of thegantry 1, a patient's bed 8 turnably suspended from and supported on theirradiation field forming device 5, a support frame 14 for rotatablysupporting the rotating rod 13, and a gantry rotating drive motor 9 forgenerating a rotating drive force for the rotating rod 13.

The transport equipment 4 provided on the gantry 1 comprises, forexample, deflecting electromagnets, four-pole electromagnets or the like(all these are omitted from the figure), and permits beams emitted fromthe synchrotron 101 to be injected coaxially of the center 2 of rotation(axis of rotation) of the gantry 1. The injected beams are first bent inorbit by the deflecting electromagnets to be transported to a side ofthe irradiation field forming device 5 with the betatron oscillationadjusted by the four-pole electromagnets.

Also, the irradiation field forming device 5 comprises, for example,scanning electromagnets, a scattering body, a ridge filter, a bolus,collimator, or the like (all these are omitted from the figure) to forman irradiation field so that intensity and configuration of beams assumevalues set by the treatment planning device 103. That is, beamsconducted into the irradiation field forming device 5 first pass betweenmagnetic poles of the scanning electromagnets to be deflected in amanner to provide for circular scanning in a position of the affectedpart, and then are scattered by the scattering body to be enlarged indiameter, after which the ridge filter gives energy of beams adistribution conformed to a thickness of the affected part. Thereafter,beams are input into the bolus to generate an energy distributionconformed to a lower configuration of the affected part, and furtherformed into a horizontal configuration of the affected part to beirradiated on the affected part.

At this time, according to a feature of the invention, the irradiationfield forming device 5 is arranged eccentrically (substantiallyvertically in a reference position of rotation (a state shown in FIG. 1)described later) such that its axis of irradiation (axis of irradiation)6 passes a different position from the center 2 of rotation of thegantry 1 (in other words, does not pass the center 2 of rotation). Also,the transport equipment 4 when being in the reference position ofrotation correspondingly swings beams incident from the synchrotron 101upwardly obliquely toward a radially outer periphery, then transportsthe beams in an axial direction of the gantry 1, and directs the beamssubstantially vertically downward at a distal end to make the beamsincident upon the irradiation field forming device 5. In addition, acounter weight 12 intended for adjustment of weight balance is fixed ona side of the rotating rod 13 opposite to the gantry 1.

The transport equipment 4 and the irradiation field forming device 5 aremounted on the rotating support structure 3 fixed to the rotating rod 13(alternatively, the rod 13 may be fixed to the support frame 14 and therotating support structure 3 may be supported to be rotatable about therotating rod 13). Thereby, the gantry 1 composed of the rotating rod 13,the rotating support structure 3, the transport equipment 4 and theirradiation field forming device 5 are unitary together to be rotatableabout the center 2 of rotation.

With the irradiation device 102 in the embodiment, the gantry 1constructed to be rotatable about the center 2 of rotation can turn froma vertical irradiation position (=reference position, in other words, aposition where an axis of the counter weight 12 forms an angle θ=0°relative to the horizontal, see FIG. 3A described later) where the axisof irradiation 6 in the irradiation field forming device 5 as shown inFIG. 1 becomes vertical, to a horizontal irradiation position (see FIG.3B described later, in other words, a position where θ=90°) where thegantry 1 is turned 90° clockwise as viewed in FIG. 1 to make the axis ofirradiation 6 horizontal). Thereby, it is possible to performirradiation in a direction in the range from irradiation on a patient Klying on the patient's bed 8 from vertically upward (corresponding toθ=0° in FIG. 3A), to irradiation from one sense of a right and leftdirection (righthand in the example in FIG. 1, FIG. 3B). At this time,since irradiation in a direction in the range from irradiation on apatient K lying on the patient's bed 8 from vertically upward, toirradiation from the other sense of the right and left direction(lefthand in FIG. 1) is made possible by having a patient K lying on thepatient's bed 8 with a head and feet reversed, the above positions arecombined to enable irradiation on a patient K from all directions(vertical irradiation to horizontal irradiation in the right and leftdirection) in the range of 180°.

In addition, with the present embodiment, the reference position ofrotation of θ=0° is set such that as shown in FIG. 1, a height from aninstallation surface D to the patient's bed 8 is minimum at a positionof θ=45° and maximum at positions of θ=0° and θ=90° (the positions areat the same level). In addition, it goes without saying that a patient Kgets on and off the patient's bed 8 in the position (θ=45°) where theheight of the patient's bed 8 is minimum.

FIG. 4 is a view showing a detailed constitution related to rotatingdriving of the gantry 1 and an essential part of the constitution shownin FIG. 1. In FIG. 4, a drive force can be transmitted to the rotatingrod 13 by connectingly providing, for example, a chain 17 or the likebetween a pulley 15 fixed on a shaft end of the rotating rod 13 and apulley 16 provided on a one shaft end (lefthand in FIG. 2) of a rotatingshaft 9 a of the gantry rotating drive motor 9 and circulatingly drivingthe chain 17.

The gantry rotating drive motor 9 is, for example, a known servomotor tobe driven by a drive command signal output from a gantry rotationcontroller 18 on the basis of a control signal from the control device100. At this time, arranged on the other shaft end (lefthand in FIG. 2)of the rotating shaft 9 a of the gantry rotating drive motor 9 and madecoaxially integral with a motor part is a rotary encoder 19 to output tothe gantry rotation controller 18 a pulse signal (in other words, adetection signal of the rotating speed of the rotating shaft 9 a) everya certain minute rotating angle.

When a direction of irradiation on the affected part of a patient K fromthe gantry 1 is to be set or modified, a control signal conformed to thedirection of irradiation is output to the gantry rotation controller 18from the control device 100. The gantry rotation controller 18 feedbackcontrols the gantry rotating drive motor 9 on the basis of a controlsignal from the control device 100 and a detection signal from therotary encoder 19 so that the gantry 1 comes to a predetermined angularposition. Thereby, the gantry 1 is rotatingly driven to theabove-mentioned set angular position to be moved to a position wherebeams can be irradiated on a patient from the above-mentioned directionof irradiation.

In addition, a known inclinometer may be provided somewhere on thegantry 1 or the counter weight 12 to input its detection signal into thegantry rotation controller 18 to feedback control the gantry rotatingdrive motor 9 on the basis of the detection signal and a control signalfrom the control device 100. In any events, when coming to apredetermined angular position, the gantry 1 is preferably stopped inthe turning position by, for example, a rotation braking brake 20provided on an outer periphery of the pulley 15.

In addition, a rotating drive source for the gantry 1 is not limited toan electric type one such as the gantry rotating drive motor 9 but canmake use of hydraulic pressure, air pressure or the like, and a driveforce transmitting system for the gantry can make use of rack andpinion, drive with a plurality of gears, belt, spring mechanism or thelike other than the above pulley system. Detection of angular positionsis not limited to an encoder but known angle meters may be used.

Meanwhile, the patient's bed 8 is constructed to be able to berotatingly driven so that the patient's bed 8 even when being in anyposition can be maintained horizontal relative to the gantry 1, whichcan assume various rotating positions about the center 2 of rotation inthe manner described above (alternatively, the patient's bed 8 can beinclined at a predetermined angle relative to the axis of irradiation6).

FIG. 5 is an enlarged view of a B part in FIG. 2, representative of adetailed support construction for the patient's bed 8. In FIG. 5, bedrotating drive motors 21, 21 (mounted in two locations in a longitudinaldirection of the patient's bed 8) are provided to be coaxial with anaxis m of rotation of the patient's bed 8 in a lower end of theirradiation field forming device 5. Shaft ends on one sides (centrallyin a right and left direction in FIG. 5) of rotating shafts 21 a of thebed rotating drive motors 21 are inserted into through holes 22 providedon bracket portions 8 a of the patient's bed 8 and fixed to the bracketportions 8 a by means of stopper members 23, whereby drive force of thegantry rotating drive motor 9 is transmitted to turn the patient's bed 8to enable changing a relative rotating angle (in other words, aninclination), which the patient's bed 8 forms relative to theirradiation field forming device 5.

The bed rotating drive motors 21 are, for example, known servomotorslike the above-mentioned gantry rotating drive motor 9 as shown in FIG.2, and driven by a a drive command signal output from a bed rotationcontroller 24 on the basis of a control signal from the control device100.

At this time, arranged on the other shaft ends (both end sides in aright and left direction in FIG. 5) of the rotating shafts 21 a of thebed rotating drive motors are rotary encoder units 19 to be madecoaxially integral with the motor parts and to output to the bedrotation controller 24 a pulse signal (a detection signal of therotating speed of the rotating shafts 21 a) every a certain minuterotating angle. When the posture of a patient K is to be set or modifiedupon setting or modification of a direction of irradiation on theaffected part of a patient K from the gantry 1, a control signalconformed to the direction of irradiation is output to the bed rotationcontroller 24 from the control device 100. The bed rotation controller24 feedback controls the bed rotating drive motors 21 on the basis of acontrol signal from the control device 100 and a detection signal fromthe encoder units 25 so that the patient's bed 8 comes to apredetermined angular position relative to the irradiation field formingdevice 5. Thereby, the patient's bed 8 is rotatingly driven to theabove-mentioned set angular position to be modified in posture to aposition where beams from the gantry 1 can be irradiated on the affectedpart from a predetermined direction of irradiation.

In addition, a known inclinometer may be provided somewhere on thepatient's bed 8 to input its detection signal into the bed rotationcontroller 24 to feedback control the bed rotating drive motors 21 onthe basis of the detection signal and a control signal from the controldevice 100. In any events, when coming to a predetermined relativeangular position, the above feedback control is preferably continuedtaking account of the shift of center of gravity caused by a subtlechange in posture of a patient K as far as a patient K is loaded on thepatient's bed 8. Also, with a view to performing irradiation of higherquality, a triaxial moving mechanism and a triaxial rotating mechanismmay be provided on the patient's bed 8.

In addition, a rotating drive source for the patient's bed 8 is notlimited to an electric type one such as the bed rotating drive motors 21but can make use of hydraulic pressure, air pressure or the like, and adrive force transmitting system can make use of rack and pinion, drivewith a plurality of gears, belt, spring mechanism or the like other thanthe above direct coupling system. Detection of angular positions is notlimited to an encoder but known angle meters may be used.

In addition, according to a feature of the invention, even when thegantry 1 is in any position (in the range of from θ=0° to 90°) in thedirection of rotation and the patient's bed 8 itself is in any positionrelative to the irradiation field forming device 5 in the direction ofrotation, the patient's bed 8 is arranged on a side opposite to thetransport equipment 4 with respect to a plane S, which contains theabove described center 2 of rotation and is substantially perpendicularto the axis of irradiation 6 (see FIG. 1 and FIGS. 3A and 3B).

Also, at this time, the patient's bed 8 and the irradiation fieldforming device 5 are preferably constructed in such a manner that theaxis m of rotation of the patient's bed 8 corresponds to an actualirradiation point 7 of beams as shown in FIGS. 6A and 6B even at thetime of vertical irradiation (a state shown in FIG. 6A; corresponding toFIG. 3A) and at the time of horizontal irradiation (a state shown inFIG. 6B; corresponding to FIG. 3B).

Further, it is desired that a X-ray receptor be installed on anextension of the axis of irradiation 6 beyond the patient's bed 8 toconstantly face the axis of irradiation 6 at front ways. Also, it isdesired that laser markers for positioning be installed in the vicinityof a patient.

(3) Therapeutic Procedure by the Charged Particle IrradiationTherapeutic System

An explanation will be given below in detail to the therapeuticprocedure by means of the charged particle irradiation therapeuticsystem constructed in the above manner and to action of the irradiationdevice 102.

The treatment planning device 103 is composed of, for example, acomputer, a plurality of displays, input device and patient's data base(the patient's data base may be separate from the device and connectedthereto via a network), and has the function of assisting a treatmentplanning work performed by a physician as a step prior to an actualirradiation. Here, the treatment planning work concretely includesidentification of the affected part, determination of irradiated regionand irradiating direction, determination of dose of radiation to apatient, calculation of dose distribution in a patient's body, and soon.

(a) Identification of the Affected Part

For example, at the time of diagnosis prior to treatment,three-dimensional picture image data for lump inside the body arebeforehand acquired by the X-ray CT examination and MRI examination.These data are numbered every patient to be preserved and managed asdigital data in the patient data base. Additionally, recorded andmanaged in the patient data base are all data required for treatment ofa patient and composed of information such as a patient's name, apatient's number, age, body height, body weight, record of medicalexamination and inspection, clinical history, therapeutic history,therapeutic data, and so on. A physician can suitably make access to thepatient data base to acquire picture image data of the above-mentionedaffected part to represent the same on a display device of the treatmentplanning device 103, and so can represent the picture image data of theaffected part as a three-dimensional picture image as viewed from anydirection or a cross sectional picture image obtained by slicing thepicture image data every depth in any direction. Also, there is providedthe function of assisting identification of the affected part throughemphasizing contrast for each picture image, painting out a region witha certain gradation as a threshold, and the like. A physician identifiesa region of the affected part while making use of these assistingfunctions.

(b) Temporary Selection of Irradiated Region and Irradiating Direction

Subsequently, a physician operates to determine an irradiated region,which envelopes the affected part and allows a suitable margin takingaccount of the possibility that the affected part is moved in the bodydue to respiration or the like. Further, a physician selects several(plural) irradiating directions (for example, in the range of from θ=0to 90°) clear of internal organs, such as backbone, of high sensitivityto radioactive rays.

(c) Determination of Irradiation Filed Profile

An irradiation field picture image as viewed from an irradiationdirection is displayed on the basis of several selected irradiationdirections, and an irradiation filed profile covering an entire lump isemphatically displayed. Also, a three-dimensional picture image isdisplayed, and a position of a maximum cross section and athree-dimensional configuration following the cross section aredisplayed. These picture images are displayed separately in a pluralityof displays in the display device. At this time, data of thethree-dimensional configuration following the maximum cross section orthe irradiation filed profile constitutes fundamental data (originaldata) for an irradiation filed, which is reshaped by the irradiationfield forming device 5, or correction of irradiation.

(d) Final Determination of Irradiation Direction, Dose of Radiation, andthe Like

Based on information of the irradiation filed profile, the treatmentplanning device 103 displays positions of respective leaf plates of thecollimator in the irradiation field forming device and a picture imageof a maximum cross section of the irradiation filed in layers. At thistime, a physician determines positions of the leaf plates on the basisof the layered picture images, and the result as determined is promptlyreflected on the display of the display device. Thereafter, based oninformation of positional setting of the leaf plates, the treatmentplanning device 103 simulates a radiation dose distribution in the bodythrough calculation to display a result of the calculated radiation dosedistribution on the display device. At this time, irradiation parameterssuch as radiation dose, radiation energy, or the like are given by aphysician, the simulation is implemented with respect to severalirradiation directions selected previously, and that irradiationdirection, for which the most preferable result is obtained, is finallyselected by a physician.

In addition, information of setting of the selected irradiationdirections, information of set positions of the leaf plates of thecollimator based thereon, data of irradiation correcting tools, andirradiation parameters are preserved as therapeutic data peculiar to apatient in the patient data base.

(e) Rotating Driving of the Gantry and the Patient's Bed

The control device 100 comprises an input device and a display device asinterfaces operated by a user, and can acquire treatment data of apatient including information of setting of irradiation directionsdetermined by the treatment planning device 103, through networkconnection from the patient data base subordinating to the treatmentplanning device 103 and display the same on the display device to havethe same ascertained by a physician.

At the time of actual irradiation, the control device 100 outputs, basedon the above information of setting of irradiation directions, commandsof starting rotation of the gantry 1 and the patient's bed 8 to thegantry rotation controller 18 and the bed rotation controller 24 aimingat a target point 10 of the affected part (see FIGS. 1 and 2) positionedon the axis of irradiation 6 and serving as an irradiation target pointfor implementation of irradiation and responding to input of beginningof irradiation treatment from, for example, a physician or aradiological technician engaged in assisting a physician's treatment onthe basis of the above treatment plan.

The gantry rotation controller 18 serves to output a necessary controlcommand to the gantry rotating drive motor 9, which constitutes alow-order mechanism, in accordance with a command from the controldevice 100, and feedback controls, upon receipt of the rotation startingcommand from the control device 100, the gantry rotating drive motor 9in the manner described above to turn the gantry 1 about the rotatingrod 13 (more specifically, on the center 2 of rotation) to move the sameto a predetermined position of the set direction of rotation (setangle). At this time, assuming that a spacing between an actualirradiation point 7 and the center 2 of rotation is d for the targetpoint 10 of rotation, the irradiation point 7 moves in the range of fromθ=0° to 900 drawing an arc of a radius d about the center 2 of rotation(see FIG. 1).

Likewise, the bed rotation controller 24 serves to output a necessarycontrol command to the bed rotating drive motors 21, which constitutes alow-order mechanism, in accordance with a command from the controldevice 100, and feedback controls, upon receipt of the rotation startingcommand from the control device 100, the bed rotating drive motors 21 inthe manner described above to turn the patient's bed 8 relative to theirradiation field forming device 5 to maintain the patient's bed 8 in ahorizontal state (alternatively, the patient's bed is set at apredetermined inclination).

In addition, in the above procedure, information of present position ofand drive state of the gantry 1 controlled by the gantry rotationcontroller 18, and information of present position of and drive state ofthe patient's bed 8 controlled by the bed rotation controller 24 aretransmitted to the control device 100 at all times to be displayed onthe above display device of the control device 100.

In addition, the transport equipment 4 constitutes a transport means forinjecting and transporting charged particle beams toward the patient'sbed, the irradiation field forming device 5 constitutes an irradiationfield forming means for forming an irradiation field of beamstransported by the transport equipment, the rotating rod 13 constitutesa rotating shaft member, which is fixed to a rotating irradiation bodyand a central axis of which constitutes an axis of rotation, and thesupport frame 14 constitutes a support means for rotatably supportingthe rotating shaft member.

Also, the gantry rotating drive motor 9 constitutes a rotating drivemeans for rotatingly driving the rotating shaft member, the rotaryencoder 19 constitutes a rotation detecting means for detecting arotating position of the rotating shaft member, and the gantry rotationcontroller 18 constitutes a rotation controlling means for controllingthe rotating drive means in accordance with the detected result.

Further, the bed rotating drive motors 21 constitutes a bed drivingmeans for driving the patient's bed, which is rotatably suspended andsupported, and changing an inclination of the bed, the encoder units 25constitutes an inclination detecting means for detecting an inclinationof the patient's bed, and the bed rotation controller 24 constitutes aninclination controlling means for controlling the bed driving means inaccordance with the detected result.

(5) Effect of the Embodiment

The medical charged particle irradiation apparatus according to theembodiment, provided in the charged particle irradiation therapeuticsystem gives the following effect.

(5-1) Capability of Upward and Horizontal Irradiation While Suppressinga Patient's Height

For example, with the above-mentioned construction of the prior art, inwhich a rotary frame provided with an irradiation chamber capable ofturning on its axis is rotated, a position of a patient's bed in aheightwise direction is much varied with a circular motion (verticalmotion) of the irradiation chamber caused by rotation of the rotaryframe. That is, since a diameter of rotation of an irradiation bodyprovided with a transport means and an irradiation field forming meansis around, for example, 5 m, a lift distance from a lowest position ofthe patient's bed for upward irradiation to a lateral position of thepatient's bed for horizontal irradiation in the heightwise directionamounts to about 2.5 m corresponding substantially to a radius ofrotation.

In contrast, with the irradiation device 102 according to theembodiment, the axis of irradiation 6 of the irradiation field formingdevice 5 is made eccentric to pass a different position from the center2 of rotation of the gantry 1 (in other words, the axis of irradiation 6involves a predetermined angle so as not to intersect the center 2 ofrotation), whereby a position of the patient's bed 8 at the time ofupward irradiation (corresponding to the position of θ=0°) is not alowest position as in the above prior art but can rise somewhat to aposition (a righthand position in FIG. 1) in either direction laterallyof a lowest position (corresponding to the position of θ=45° in theembodiment). Also, a position of the patient's bed (corresponding to theposition of θ=90° in the embodiment) at the time of horizontalirradiation can be correspondingly made a position somewhat lowered fromthe other lateral position unlike the lateral position (the otherlateral position in accordance with the above) in the above prior art.

That is, the patient's bed 8 when the gantry 1 is turned to displace thepatient's bed from a position (θ=0°) at the time of upward irradiationto a position (θ=90°) at the time of horizontal irradiation moves fromthe position (θ=0°) at the time of upward irradiation gradually descendsto a lowest position (θ=45°)→gradually ascends to a position (θ=90°) atthe time of horizontal irradiation. In this manner, since the position(θ=0°) of the patient's bed 8 at the time of upward irradiation and theposition (θ=90°) of the patient's bed 8 at the time of horizontalirradiation are not a lowest position but can be made a positionsomewhat higher than the lowest position, variation (in other words,difference of height between the lowest position (θ=45°) and theposition (θ=0°) at the time of upward irradiation or the position(θ=90°) at the time of horizontal irradiation) in a heightwise positionof the patient's bed in displacements, that is, the position at the timeof upward irradiation →the lowest position →the position at the time ofhorizontal irradiation can consequently be suppressed considerably.

Meanwhile, in the gantry 1, the transport equipment 4 having chargedparticle beams injected at the center 2 of rotation of the gantry 1 oncedirects (swings up) the beams to a diametrically outer peripheral sideas conceptionally shown in FIG. 7, then transports the beams apredetermined distance in the axial direction of the gantry 1, and againdirects the beams to the diametrically inner peripheral side of thegantry 1 at a distal end to inject the beams into the irradiation fieldforming device 5. The plurality of deflecting electromagnets fordirecting (deviating) the beams are provided on the beam transport pathas described above. With such construction, in the case where thetransport equipment 4 is provided in a substantially cylindrical-shapedrotary frame rotatably supported, the patient's bed 8 is arranged at thecenter 2 of rotation of the gantry, and the irradiation field formingdevice is arranged on the diametrically outer peripheral side thereof asin the above prior art, a distal end of the transport equipment 4 ispositioned, as conceptionally shown in FIG. 8A, near the diametricallyouter peripheral side thereof than the irradiation field forming device5 in order to inject beams into the irradiation field forming device 5.As a result, the transport equipment 4 is shaped to be considerablyenlarged toward the outer peripheral side of the gantry 1, so that thegantry 1 is increased in diameter of rotation.

Meanwhile, in the case where the axis of irradiation 6 passes throughthe rotating shaft of the gantry and the patient's bed 8 is arrangednearer the diametrically outer peripheral side thereof (an opposite sideof the transport equipment 4) than a position of the center 2 ofrotation of the gantry in the rotating frame as conceptionally shown inFIG. 8B, the irradiation field forming device 5 can also be made offsetan amount, by which the patient's bed 8 is offset toward the oppositeside of the transport equipment 4, toward the opposite side of thetransport equipment 4 (a lower side in FIG. 8B), as understood incomparison with FIG. 8A, with the result that the above enlargementtoward the outer peripheral side thereof in the diametrical directioncan be reduced. As a result, the gantry 1 can be reduced by such amountin diameter of rotation as shown in FIG. 8B.

Also, in the embodiment, the same effect as in comparative example shownin FIG. 8B can be obtained since the patient's bed 8 is arranged nearerthe opposite side of the transport equipment 4 than the position of thecenter 2 of rotation, more specifically, on the opposite side of thetransport equipment 4 (a lower side in FIG. 8B) with respect to theplane, which contains the above center 2 of rotation and issubstantially perpendicular to the axis of irradiation 6.

As described above, according to the embodiment, the above action ofreducing the gantry 1 in diameter of rotation is added to the action ofsuppressing heightwise variation in a position of the patient's bed 8between the position (θ=0°) at the time of upward irradiation and theposition (θ=90°) at the time of horizontal irradiation, whereby theirmultiplied effect can suppress heightwise variation of the patient's bed8 (difference of height from the position θ=45° to the position θ=0° or90°) to around 1.5 m at maximum through suitable setting of positions ofrespective parts such as eccentric dimension of the axis of irradiation6 or the like. Thereby, even in a state, in which the patient's bed 8 isin the highest position (the position θ=0° at the time of upwardirradiation and the position θ=90° at the time of horizontalirradiation), a physician or a technician can perform the irradiationpreparing/ascertaining work or the like while standing on a floorwithout any specific separate device, so that convenience can beconsiderably improved. Also, since the heightwise position of thepatient's bed 8 is suppressed, a patient can be enhanced in safety.

(5-2) Improvement in Accuracy of Irradiation or the Like

In the case of that construction, in which respective constituentelements of the gantry 1 are arranged in, for example, the substantiallycylindrical-shaped rotary frame as illustrated in the above paragraph(5-1) with reference to FIG. 8A, large-sized and heavy articles such asthe transport equipment 4, the irradiation field forming device 5 or thelike are supported by the substantially cylindrical-shaped rotary frameprovided with no shaft. Therefore, it is difficult to suppressgeneration of that deformation, such as flexure or the like, in therotary frame, which is caused by their weights, and consequently it isdifficult to prevent that degradation in relative positional accuracybetween the target point 10 of rotation and the irradiation point 7,which is attributable to the flexure or the like.

In contrast, with the irradiation device 102 according to theembodiment, the construction with a shaft, in which the respectiveconstituent elements of the gantry 1 are fixed to the above rotating rod13, can reduce generation of flexure or the like in comparison with theabove construction, in which load is born by the rotary frame. Thereby,degradation in relative positional accuracy between the target point 10and the irradiation point 7 can be prevented and irradiation accuracycan be improved.

The construction with a shaft, in which load of all the members of thegantry 1 can be supported by the rotating rod 13, can take effect inreducing the diametrical dimension of the gantry 1 as compared with thecase of supporting by means of the substantially cylindrical-shapedrotary frame provided with no shaft, shown in FIG. 8A.

(5-3) Miniaturization of a Building

As described in the above paragraph (5-1), according to the embodiment,the charged particle irradiation apparatus 102 can be reduced in size asa whole since the diameter of rotation (in other words, a diametricaldimension) and axial dimension of the gantry 1 can be reduced. Thereby,for example, in the case where the synchrotron 101 is installed on anordinary floor surface F with its beam injecting axis corresponding tothe center 2 of rotation of the gantry 1, it is not required that alevel of the installation surface D, on which the irradiation apparatus102 is installed, be so much lower than the floor surface F, and asemi-underground construction will do. Accordingly, while for example,the constitution shown in FIG. 8A requires a three-floor construction orso as a building for receiving the synchrotron 101 and the irradiationapparatus 102, the entire building can be considerably reduced indimension (in particular, heightwise dimension).

(5-4) Lightening of the Irradiation Apparatus

The construction, in which the irradiation field forming device 5 ismade offset and enlargement of the transport equipment 4 iscorrespondingly reduced as described in the above paragraph (5-1), makesit possible to make the position of gravity of the entire irradiationapparatus 102, which is provided with the transport equipment 4 and theirradiation field forming device 5, close to the center 2 of rotation ascompared with the constitution shown in, for example, FIG. 8A. Thereby,the necessity of the counter weight 12 required for balancing of weightis decreased, and so lightening of the irradiation apparatus 102 can beachieved correspondingly.

(5-5) Others

{circumflex over (1)} Utilization of unused space

With the irradiation device 102 in the embodiment, a large space isensured above a patient K in the position θ=90° at the time ofhorizontal irradiation (see FIGS. 1 and 3B), so that a X-ray CTexamination apparatus or the like is installed in this position toperform CT photographing without having a patient K getting off thepatient's bed 8. In addition, as measures of utilizing this space, adevice for charging and setting equipments, such as bolus, collimator,or the like, which are provided on the irradiation field forming device5 and must be exchanged or set every patient, can be mounted in theabove position.

{circumflex over (2)} No Weight Limit for the Bed

In the case of that construction, in which respective constituentelements of the gantry 1 are arranged in, for example, the substantiallycylindrical-shaped rotary frame shown in, for example, FIG. 8A, asdescribed in the above paragraph (5-2), it is desirable to make thepatient's bed 8 as lightweight as possible in terms of suppressingdegradation in accuracy of irradiation. In contrast, with theirradiation device 102 in the embodiment, it is possible to fulfill theduties as a counter weight for the transport equipment 4 and theirradiation field forming device 5, so that a heavy load is notproblematic and therefore there is no weight limit.

In addition, the above embodiment uses the drive force of the gantryrotating drive motor 9 to forcedly rotatingly drive the patient's bed 8in order to maintain the patient's bed 8 in a horizontal stateirrespective of, for example, a rotating position of the gantry 1 (θ=0°to 90°), but is not limited thereto. That is, the patient's bed 8 may befreely rotatably suspended from and supported by a lower end of theirradiation field forming device 5, and a heavy object (weight or thelike) may be provided on the patient's bed 8 to have its weightnaturally maintaining the patient's bed 8 in a horizontal posture. Also,it goes without saying that the patient's bed 8 be manufactured from aheavy material to be made a heavy object. In these cases, the functionas a counter weight for the transport equipment 4 and so on as describedin the above {circumflex over (2)} is further increased.

Also, according to the above embodiment, the rotating angle of thegantry 1 is in the range of from θ=0° to 90° but is not limited thereto.That is, a little wider range, for example, θ=0° to 120°, can be adoptedby suitably setting the positional relationship between the center 2 ofrotation of the irradiation device 102 and the irradiation point 7.Also, on the contrary, a range narrower than 90° can be adopted, inwhich case, for example, horizontal irradiation and irradiation in adirection close thereto suffice to be made by inclining the patient'sbed 8 a little angle (in the order of not compelling a patient to assumean unnatural posture) for compensation for insufficiency in the rotatingangle of the gantry 1. In the examination performed by the inventors ofthis application, when at lease rotation in the range of from θ=0° to60° is possible, adjustment of an inclination by means of rotatingdriving of the patient's bed 8, and position and direction, in which apatient is loaded, make it possible to actually irradiate chargedparticles on the affected part from a sufficiently multiplicity ofangles.

According to the invention, the action of suppressing heightwisevariation in a position of the patient's bed 8 from the position at thetime of upward irradiation to the position at the time of horizontalirradiation, and the action of reducing the rotary irradiation body indiameter of rotation present a multiplied effect to suppress heightwisevariation of the patient's bed (difference of height) to around 1.5 m atmaximum provided that positions of respective parts such as eccentricdimension or the like are suitably set. Accordingly, even in a state, inwhich the patient's bed is in the highest position (the position at thetime of upward irradiation and the position at the time of horizontalirradiation), a physician or a technician can perform the irradiationpreparing/ascertaining work or the like while standing on a floorwithout any specific separate device, so that convenience can beconsiderably improved. Also, since the heightwise position of thepatient's bed is suppressed, a patient can be enhanced in safety.

Also, the charged particle irradiation apparatus can be reduced in sizeas a whole since the diameter of rotation (in other words, a diametricaldimension) and axial dimension of the rotary irradiation body can bereduced. Thereby, there is produced an effect to enable considerablyreducing a space, in which a charged particle irradiation apparatus isordinarily installed having a beam injecting axis corresponding to acenter of rotation of a rotating irradiation body, and a dimension (inparticular, a heightwise dimension) of an entire building for receivingthe charged particle irradiation apparatus and a charged particlegenerating apparatus.

Further, the construction, in which the above irradiation field formingmeans is made offset and enlargement of the transport means iscorrespondingly reduced, makes it possible to make the position ofgravity of the entire medical charged particle irradiation apparatusclose to the center of rotation as compared with the constitution, inwhich an irradiation field forming means is diametrically arranged on anouter peripheral side of a patient's bed with a position, in which apatient's bed is arranged, as a position of an axis of rotation of arotating irradiation body. Thereby, there is produced an effect that,for example, a counter weight required in the above-mentionedconstruction is made unnecessary, or the necessity therefor is reduced,and lightening of the medical charged particle irradiation apparatus canbe achieved correspondingly.

1-7. Cancelled
 8. A medical charged particle beam irradiation apparatusfor irradiating charged particle beam to an irradiation targetcomprising: a rotating gantry; an irradiation field forming device forirradiating said charged particle beam to said irradiation target, beingarranged such that said irradiation field forming device passes aposition different from a rotational axis of said rotating gantry; abeam transport device for transporting said charged particle beam tosaid irradiation field forming device, being provided to said rotatinggantry; and a bed for supporting said irradiation target, said bed beingrotatably provided relative to said irradiation field forming device, apointed end of said irradiation field forming device is positioned underthe level of the rotational axis of said rotating gantry in a state thatsaid irradiation field forming device is perpendicular to the axis.
 9. Amedical charged particle beam irradiation apparatus according to claim8, further comprising a rotating device for rotating said bed, and acontrolling device for controlling said rotating device to maintain saidbed in a horizontal state.